Weldable laminated structure and method of welding

ABSTRACT

A laminate structure and method of welding the laminate structure is provided. The laminate structure includes a first metal sheet having a first thickness, a second metal sheet having a second thickness, and an adhesive core made of an adhesive material also described as a viscoelastic adhesive material. The adhesive core is disposed between and bonded to the first and second metal sheets. The first and second metal sheets are made of an aluminum based material. The adhesive core includes a plurality of electrically conductive filler particles dispersed in the adhesive materials. The filler particles are made of a first filler material and at least a second filler material which is a different material than the first filler material.

CROSS REFERENCES TO RELATED APPLICATIONS

This Application claims the benefit of International Patent ApplicationPCT/US2016/029974, filed on Apr. 29, 2016, and of International PatentApplication PCT/US2015/028801, filed on May 1, 2015, which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a laminate of metal sheets including acore layer disposed between and connected to the metal sheets, andspecifically, to a laminate including metal sheets of an aluminummaterial.

BACKGROUND

A laminate sheet made of metal sheets including a viscoelastic coredisposed therebetween is less dense than a monolithic (solid) metalsheet of the same thickness. The monolithic metal sheet may be noisier,e.g., may exhibit less favorable noise-vibration-harshness (NVH)characteristics as compared with the laminate sheet, due to the modulusdifferences of the materials, where the monolithic metal sheet is moresusceptible to vibration and resonance and more sensitive to frequencymanagement than the laminate sheet. Further, structural componentsformed from sheet material can include complex shapes such as bends,ribs, beads, offsets, depressions, channels, contours and the like,which can be added to improve stiffness and/or bending strength to thestructural component. Such complex features can protrude from the sheet,increasing the packaging space required by the structural component andincreasing radiated noise through the monolithic component. As such,structural components formed from monolithic metal sheet often requiremodification by adding damping coatings and/or damping componentry suchas damping patches to provide acceptable NVH behavior. Such addedtreatments, coatings and/or damping componentry add cost and weight tothe monolithic component. Accordingly, the total weight of a structuralcomponent made of a laminate structure is substantially less than thetotal weight of a structural component made of a monolithic sheet andsubsequently treated with added damping coatings or damping componentry.

Monolithic metal sheet and monolithic structural components formed frommonolithic sheet can be joined by welding to other metal components.Welding of laminate sheet and welding of laminate components formed fromlaminate sheet differs from welding of monolithic sheet, due to theinsulating (non-conductive) characteristics of the viscoelastic layer ofthe laminate sheet which inhibits current flow through the weld zoneduring welding, and liquefying and/or vaporizing of the viscoelasticlayer which can occur during the welding process, where the liquefiedand/or vaporized viscoelastic material can contaminate the weld beingformed and/or contribute to the formation of porosity in the weld.Porosity and/or contamination in the weld can decrease the durability,fatigue strength and overall integrity of the weld.

As such, it is desirable to provide a laminate sheet material which maybe formed into a laminate structural component which, relative to amonolithic structural component formed from a monolithic metal sheet,exhibits relatively lower total weight and relatively better dampingcharacteristics, and is attachable to other components by welding.

SUMMARY

A weldable laminate structure and method of forming a welded joint isdescribed. The laminate structure, which includes a viscoelasticadhesive layer between and bonding aluminum sheets, is advantaged bybeing formable into a structural component which provides desired levelsof vibration damping, sound transmission loss, structural separation,etc. at a lower total weight relative to a structural component formedof a monolithic metal sheet, by eliminating the treatments, such assound dampening coatings or patches, which must be added to thestructural component made from monolithic aluminum to achieve thedesired NVH performance. A structural component, as that term is usedherein, refers to a component formed from sheet material which has acomplex shape, e.g., a shape other than flat sheet, and is used in astructural application. The structural component can be formed from thelaminate structure, by any forming process suitable for formingmonolithic sheet material into a structural component, including, by wayof non-limiting example, stamping, extrusion, blanking, bending, etc.,such that the better damping performance and total system weightreduction can be achieved by forming the structural component from alaminate structure without requiring significant change to the formingprocess used to form the structural component formed from monolithicaluminum.

For example, the complex shape of a structural component can be definedby one or more features, such as one or more of a bend, rib, aperture,bead, offset, chamfer, depression, channel, curve, contour, extrudedportion, or other feature formed into the laminate structure to definethe structural component. As such, the laminate structure describedherein can be formed into structural components where there is aparticular need for noise dissipation, vibration and/or sound damping,structural separation, thermal insulation and/or acoustic absorption,for example, between spaces or areas separated by the structuralcomponent(s) formed of the laminate structure. The term “structuralcomponent” is non-limiting, such that a structural component may havenominal or minimal load bearing requirements. In a non-limiting example,the laminate structure described herein is formable into structuralcomponents for vehicle applications, such as close-out panels, alsoknown as dash panels or floor pans, which provide structure to thevehicle by separating, respectively, the engine compartment or trunkcompartment from the passenger compartment. Other non-limiting examplesof vehicle structural components which may be formed from the laminatestructure include wheel wells, transmission tunnel covers, cowl plenums,etc.

A laminate structure and method of forming is provided. The laminatestructure includes a first metal sheet having a first thickness, asecond metal sheet having a second thickness, and an adhesive corehaving an adhesive thickness. The adhesive core is disposed between andbonded to the first and second metal sheets. The first and second metalsheets are made of an aluminum based material and the adhesive core ismade of an adhesive material which may also be described herein as aviscoelastic adhesive material. The viscoelastic adhesive material, in anon-limiting example, can be made of one of a phenolic modified rubbermaterial, an acrylic based material, and a polyester based material.

In one example, the laminate structure is a weldable laminate structureformed by including a plurality of electrically conductive fillerparticles dispersed in the adhesive material of the core layer. Thefiller particles are made of a first filler material and a second fillermaterial which is a different material than the first filler material,where at least one the first and second filler materials has a fillerelectrical resistivity greater than the aluminum electrical resistivity.The plurality of electrically conductive filler particles are dispersedin the adhesive core to define a conduction path by which an electricalcurrent applied to one of the first and second metal sheets is conductedthrough the adhesive core to the other of the first and second metalsheets to generate a resistive heat which is sufficient to at leastpartially melt the first and second metal sheets in a weld zoneincluding the conduction path. The percentage weight of the fillerparticles is in a range of about 12% to 49% of the total weight of theadhesive core. The volume percent of the filler particles is less thanabout 15% of the total volume of the adhesive core. A method of weldingthe laminate structure formed with the electrically conductive fillerparticles is provided.

As used herein “substantially,” “generally,” and other words of degreeare relative modifiers intended to indicate permissible variation fromthe characteristic so modified. It is not intended to be limited to theabsolute value or characteristic which it modifies but rather possessingmore of the physical or functional characteristic than its opposite, andpreferably, approaching or approximating such a physical or functionalcharacteristic. As used herein with respect to any disclosed values orranges, the term “about” indicates that the stated numerical valueallows for slight imprecision, e.g., reasonably close to the value ornearly, such as ±10 percent of the stated values or ranges. If theimprecision provided by the term “about” is not otherwise understood inthe art with this ordinary meaning, then “about” as used hereinindicates at least variations that may arise from ordinary methods ofmeasuring and using such parameters. In addition, disclosure of rangesincludes disclosure of all values and further divided ranges within theentire range.

The above features and advantages, and other features and advantages, ofthe present teachings are readily apparent from the following detaileddescription of some of the best modes and other embodiments for carryingout the present teachings, as defined in the appended claims, when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a cross-section of a first examplelaminate structure including a core layer disposed between aluminumsheets;

FIG. 2 is a schematic view of a cross-section of a second examplelaminate structure including a core layer disposed between aluminumsheets;

FIG. 3 is a schematic view of a cross-section of a third examplelaminate structure including a core layer disposed between aluminumsheets;

FIG. 4 is a schematic view of a cross-section of a fourth examplelaminate structure including a core layer disposed between aluminumsheets; and

FIG. 5 is a schematic cross-sectional view showing a weld zone during awelding operation to form a welded assembly including a laminatestructure and a metal component.

DETAILED DESCRIPTION

The elements shown in FIGS. 1-5 are not necessarily to scale orproportion, and the arrangement of elements shown in FIGS. 1-5 are notintended to be limiting. Accordingly, the particular dimensions andapplications provided in the drawings presented herein are not to beconsidered limiting. Referring to the drawings wherein like referencenumbers represent like components throughout the several figures, thereis shown in FIGS. 1-5 a laminated material generally indicated at 100,also referred to herein as a laminate structure or as a laminate. Thelaminate 100 includes opposing metal sheets 12, 14 which are connectedby a core layer 10 disposed therebetween. Each of the metal sheets 12,14 is made of an aluminum based metal. The term “sheet” as used hereinin the context of aluminum materials is understood as being a rolledaluminum alloy product with a uniform thickness of less than 6 mm. Byway of non-limiting example, each of the metal sheets 12, 14 may bereferred to herein as a skin, metal layer, aluminum sheet, substrate,and/or base substrate. The core layer 10 includes an adhesive core 16which has NVH characteristics such that the core layer 10 in combinationwith the aluminum sheets 12, 14 provide a laminate structure 100 whichis characterized as a vibration damping material. The adhesive core 16may also be referred to herein as a viscoelastic core 16, and/or theadhesive core 16 may be characterized as being formed of a viscoelasticmaterial 38 (see FIG. 5) and/or having viscoelastic properties at thetarget operating temperature range of the laminate, such that theviscoelastic core 16 substantially defines the damping properties of thelaminate structure 100. The core layer 10 is disposed between thealuminum sheets 12, 14 such that the core layer 10 spans substantiallythe entirety of (i.e., is coextensive with) the metal layer 12 and themetal layer 14, adhering (i.e., rigidly attaching) the two aluminumsheets 12, 14 together such that the core layer 10 is constrained by themetal layers 12, 14. Notably, the laminate structure 100 may includeadditional layers such as additional substrate layers and coatinglayers, and the core layer 10 may include a plurality of layersincluding one or more adhesive layers, sound-damping viscoelasticlayers, coating layers, electrically or thermally conductive layers,corrosion prevention layers, etc. such that it would be understood thatthe examples shown in FIGS. 1-5 are illustrative and are not intended tobe limiting.

The laminate structure 100 described herein may be formed intostructural components where there is a particular need for enhancingstructural reinforcement, vibration and/or sound damping, thermalinsulation and/or acoustic absorption, for example, between spaces orareas separated by the structural component(s) formed of the laminatestructure 100. The laminate structure 100 described herein, includingaluminum sheets 12, 14 and core layer 10, is advantaged by beingformable into a structural component which provides desired levels ofvibration damping, sound transmission loss, structural separation, etc.at a substantially lower weight relative to a structural componentformed of a steel based material. The laminate structure 100 isadvantaged by being formable into a structural component which providessignificantly improved levels of vibration damping, sound transmissionloss, etc. at an equal or lower weight relative to a structuralcomponent formed from a monolithic metal sheet, and without requiringadded treatments, such as sound dampening coatings or patches, toachieve the desired NVH performance. A structural component, as thatterm is used herein, refers to a component formed from sheet materialwhich has a complex shape, e.g., a shape other than flat sheet, and isused in a structural application. For example, the complex shape of astructural component can be defined by one or more features, such as oneor more of a bend, rib, aperture, bead, offset, chamfer, depression,channel, curve, contour, extruded portion, or other feature formed intothe laminate structure to define the structural component. The formedfeatures defining a structural component formed from the laminatestructure 100 create discontinuities in the laminate structure 100 whichchange the modal frequencies of the laminate structure 100. For example,discontinuities created by formed features in a component formed fromthe laminate structure 100 modify and/or change resonant frequencies ofsound waves transmitted through the laminate structure 100, relative tothe transmission of sound waves through a monolithic (solid) material.As such, the laminate structure 100 described herein can be formed intostructural components where there is a particular need for noisedissipation, vibration and/or sound damping, thermal insulation and/oracoustic absorption, for example, between spaces or areas separated bythe structural component(s) formed of the laminate structure 100. Theterm “structural component” is non-limiting, such that a structuralcomponent can include components having formed features which havenominal or minimal load bearing requirements, although it would beunderstood that formed features such as ribs, channels, beads, or othergeometric formed features included in a component formed from thelaminate structure 100 can increase the stiffness and/or rigidity of thecomponent. In a non-limiting example, the laminate structure 100described herein is formable into structural components for vehicleapplications, such as close-out panels, also known as dash panels orfloor pans, which provide structure to the vehicle by separating,respectively, the engine compartment or trunk compartment from thepassenger compartment. Other non-limiting examples of vehicle structuralcomponents which may be formed from the laminate structure 100 includewheel wells, transmission tunnel covers, floor pans, cowl plenums, etc.In a non-limiting example, the core layer 10 may be electricallyconductive and/or the aluminum sheet 12, 14 may be coated such that thelaminate structure 100 can be joined by welding to another metalliccomponent 50 (see FIG. 5).

In a preferred example the aluminum based material comprising aluminumsheets 12, 14 is one of a 5xxx and 6xxx series aluminum alloy havingelongation greater than about 15%, preferably greater than about 20%,and more preferably having an elongation of at least about 25%, andhaving an n value of at least 0.1 and an r value of at least 0.8, wherethe n and r values characterize formability of the aluminum sheet 12,14. The “n value” as used herein is understood as being the strainhardening exponent obtained by calculating the slope of the true stressand true strain curve of the material, where it is understood thatincreasing the n value increases the formability of the material. The “rvalue” as used herein is understood as being the Lankford value, alsoreferred to as the Lankford coefficient, plastic strain ratio, and/orplastic anisotropy factor, and is a measure of the ratio of the truewidth (or lateral) strain to the true thickness strain in a tensile testof the aluminum sheet 12, 14. The r value indicates the capacity of analuminum sheet to resist thinning, where it is understood that thehigher the r value, the greater the resistance to thinning during deepdrawing. By way of example, a 5xxx or 6xxx series aluminum alloy can beused for aluminum sheets 12, 14 to provide high elongation and a heatstable structure such that the base substrates, e.g., the aluminumsheets 12, 14, provide strength and stiffness while being formable, forexample, by stamping, extrusion, deep drawing, etc. The aluminummaterial forming the aluminum sheets 12, 14 may be ¼ hard or lower, suchthat the aluminum sheets 12, 14 are readily formable. For example, thealuminum sheets 12, 14 may be provided in an annealed temper conditionalso known as an “OT” temper, or in a strain hardened tempered ¼ hardcondition also known as an “H2” temper. In one example, a laminatestructure 100 usable for forming automotive components such as dashpanels is formed of aluminum sheets 12, 14 of a 6xxx series aluminumalloy provided with an OT temper, such that the laminate structure 100is readily formable by pressing and/or stamping into complex shapes suchas dash panels, and is heat treatable, for example, during paint bakingof the dash panels and/or vehicle including the dash panels formed fromthe laminate structure 100. The example of a 5xxx or 6xxx seriesaluminum alloy material used for forming aluminum sheets 12, 14 isnon-limiting, and it would be understood that other aluminum alloys maybe used to form aluminum sheets 12, 14.

By way of non-limiting example and referring to FIG. 1, the thicknessT1, T2 of each aluminum sheet 12, 14 is in the range of about 0.4 mm to2.0 mm. In a preferred example, the thickness T1, T2 of each aluminumsheet 12, 14 is in the range of about 0.5 to 1.0 mm. In a more preferredexample, the thickness T1, T2 of each aluminum sheet 12, 14 is withinthe range of about 0.5 mm to 0.8 mm. The thickness T1, T2 of thealuminum sheets 12, 14 may be, but is not required to be, the samethickness. For example, the thickness T1 of aluminum sheet 12 may differfrom the thickness T2 of aluminum sheet 14 as required by a particularuse of the laminate structure 100, and/or as required to form aparticular component from the laminate structure 100 and/or to providefunctional characteristics such as strength, stiffness, etc. required bythe particular component formed from the laminate structure 100. Thecombined (total) thickness of the aluminum sheets 12, 14 and theadhesive core 16 is controlled such that the laminate structure 100 ischaracterized by an n value of at least 0.1, an r value of at least 0.8,an adhesive strength as measured by T-peel of at least 10pounds-force/inch and a lap shear strength of at least 2 mega-Pascalsuch that the laminate structure 100 is formable into structurecomponents by stamping, bending, extrusion and the like withoutseparation of the adhesive core 16 from the aluminum sheets 12, 14 orfracturing of the aluminum sheets 12, 14. The examples are illustrativeand non-limiting, and it would be understood that one of the aluminumsheets 12 could be a different aluminum material, temper, and/orthickness than the other aluminum sheet 14.

The core layer 10 is disposed between the aluminum sheets 12, 14 suchthat the core layer 10 spans substantially the entirety of (i.e., iscoextensive with) the metal layer 12 and the metal layer 14. Thelaminate structure 100 is formed by laminating the metal sheets 12, 14with the core layer 10 disposed therebetween such that the core layer 10adheres (i.e., rigidly attaches) the two aluminum sheets 12, 14together. The core layer 10 includes an adhesive core 16, whichsubstantially defines and/or provides the NVH (noise, vibration,harshness) and damping performance characteristics of the laminatestructure 100. The core layer 10 and/or the adhesive core 16 hassufficient adhesive properties to attach the two aluminum sheets 12, 14to each other, and has viscoelastic properties such that it dissipatesvibrational energy by converting the vibrational energy into thermalenergy through internal shearing of the adhesive material 38.

Referring again to FIG. 1, in a non-limiting example the adhesive core16, which provides the NVH performance, e.g., acts as the damping layerand attaches the aluminum sheets 12, 14 to each other to form thelaminate structure 100. The adhesive core 16 acts as the damping layerby converting sound energy into heat via shear action of the adhesivematerial 38 forming the adhesive core 16, and also acts to hold thealuminum sheets 12, 14 together during and after forming of a componentfrom the laminate structure 100. The adhesive core 16 may be formed of acombination of one or more of adhesive materials 38 including one ormore of an acrylic, polyester, polyacrylate, phenolic, rubber and/orurethane based material. In a preferred example, the adhesive core 16 isformed of an adhesive material 38 which is a viscoelastic material suchas a phenolic modified rubber adhesive, a rubber phenolic blend, or arubber-based viscoelastic material. In other examples the adhesive core16 is formed of one of an acrylic material, an acrylic rubber hybridmaterial, a polyester material including a cross-linking agent, a rubberphenolic material, a polyester rubber phenolic material, a polyacrylatematerial, a polyester-based acrylic material, and a rubber phenolicblend. The adhesive core 16 may be applied to the aluminum sheets 12, 14to provide a dry film thickness (DFT), e.g., an adhesive thickness T3shown in FIG. 1, of the adhesive core 16 within the range of about0.0005 inches to 0.0030 inches (approximately 0.013 millimeters (mm) to0.076 mm), where the damping performance of the laminate structure 100and the thickness T3 of the adhesive core are related and dependent uponthe metal layer mass and effective shear achieved with the core. In apreferred example to achieve the desired damping performance of thelaminate structure 100, the thickness T3 of the adhesive core 16 iswithin the range of about 0.001 inches to 0.0020 inches (0.025 mm to0.0508 mm). In a more preferred example, the thickness T3 of theadhesive core 16 is within the range of about 0.0008 inches to 0.0013inches (0.025 mm to 0.03 mm). In a most preferred example, the thicknessT3 of the adhesive core 16 is less than 0.0010 inches (<0.025 mm),and/or within the range of about 0.0008 inches to 0.0012 inches (0.020mm to 0.030 mm).

The adhesive material 38 forming the adhesive core 16 may be applied toone of the aluminum sheets 12, 14 in a single layer prior to laminatingthe aluminum sheets 12, 14 together with the adhesive core 16therebetween to form the laminate structure 100. In another example, theadhesive material 38 forming the adhesive core 16 may be applied in twoadhesive layers 18, 20, as shown in FIG. 2, to form the adhesive core16. For example, a first adhesive layer 18 may be applied to thealuminum sheet 14 and a second adhesive layer 20 may be applied to thealuminum sheet 12 prior to bringing the two aluminum sheets 12, 14together during laminating. In this example, the bond strength and/orpeel strength of the laminate structure 100 including the first andsecond adhesive layers 18, 20 bonded to each other is substantiallyhigher relative to a laminate structure 100 having an adhesive core 16formed from a single layer of adhesive material 38 applied to one of thealuminum sheets 12, 14 prior to laminating the lamination structure 100.

The thickness of each of the two adhesive layers 18, 20 is controlled toprovide the desired total dry film thickness T3 of the adhesive core 16in the finished laminate structure 100. By way of non-limiting example,the overall thickness of the laminate structure 100, exclusive ofexterior layers 26, 28 and isolation layers 34, may be in the range ofabout 0.813 mm to 4.76 mm. For example, a laminate structure 100 mayinclude aluminum sheets 12, 14 each having a thickness T1, T2 of 0.4 mmand an adhesive core having a thickness T3 of 0.013 mm for a totalthickness (T1+T2+T3) of 0.813 mm and an aluminum to adhesive thicknessratio of 61.5, where the aluminum to adhesive thickness ratio iscalculated as (T1+T2)/T3. In another example, a laminate structure 100may include aluminum sheets 12, 14 each having a thickness T1, T2 of 2.0mm and an adhesive core having a thickness T3 of 0.076 mm for a totalthickness of 4.076 mm and an aluminum to adhesive thickness ratio of52.6. In a preferred example, the overall thickness of the laminatestructure 100 may be in the range of about 1.45 mm to 1.66 mm. Forexample, a laminate structure 100 in the preferred thickness range mayinclude aluminum sheets 12, 14 each having a thickness T1, T2 of 0.6 mmand an adhesive core 16 having a thickness T3 of 0.025 mm for a totalthickness of 0.1.45 mm. In another preferred example, a laminatestructure 100 may include aluminum sheets 12, 14 each having a thicknessT1, T2 of 0.8 mm and an adhesive core having a thickness T3 of 0.06 mmfor a total thickness of 1.66 mm. In a preferred example, the ratio ofthe combined thickness (T1+T2) of the aluminum sheets 12, 14 to thethickness T3 of the adhesive core 16 is within the range of about 25 to50, where it would be understood that the thickness T1, T2 of thealuminum sheets 12, 14 substantially contributes the tensile strengthand rigidity to the laminate structure 100, and the thickness T3 of theadhesive core 16 substantially contributes to the dampingcharacteristics of the laminate structure 100, and where the thicknessratio influences the CLF behavior of the laminate structure 100. Theoptimal thickness for efficient vibration dissipation can be calculatedfor every metal gage used. By way of example, the laminate structure 100may be characterized by an adhesive thickness ratio in the range ofabout 8:1 to 50:1. The laminate structure 100 having an aluminum toadhesive thickness ratio ((T1+T2)/T3) of 8:1 or more is characterized bya density substantially similar to that of monolithic (solid) aluminum,which has a density of 2.7 gm/cc. In a preferred example, a laminatestructure 100 having an aluminum to adhesive thickness ratio((T1+T2)/T3) of 25:1 has a density of at least 2.56 gm/cc, such that thedensity of the laminate structure 100 is at least about 95% that ofmonolithic aluminum, contributing to the tensile properties and rigidityof the laminate structure 100. In a preferred example, the laminatestructure 100 has a density of at least 2.64 gm/cc.

The adhesive material 38 of the adhesive layers 18, 20 may be, in anon-limiting example, one of a polyester based material which may be across-linking polyester, an acrylic based material which may optionallyinclude a cross-linking agent to provide relatively higher resistance tochemical attack, and a phenolic modified rubber. In one example, theadhesive core 16 formed from the phenolic modified rubber material maybe characterized by a matrix structure including rubber dispersed in aphenolic matrix such that bond strength of the laminate structure 100 issubstantially defined by, e.g., resultant from, the bonding of thephenolic to the aluminum sheets 12, 14 and the bonding of the phenolicto the dispersed rubber particles. The adhesive material 38 may beapplied to the aluminum sheet 12, 14 by any suitable technique,including, for example, spraying, hot melt and/or rolling techniques bywhich the adhesive material 38 is applied to the aluminum sheet 12, 14,as a solvent based adhesive material, to provide full coverage of thealuminum sheet 12, 14 at the desired thickness prior to laminating thealuminum sheets 12, 14 together. In another example, the adhesivematerial 38 may be provided as a dry adhesive film and applied to one orboth of the aluminum sheets 12, 14 prior to laminating. The dry adhesivefilm can be applied, for example, in a continuous process where the dryadhesive film is interleaved between the aluminum sheets 12, 14 prior tolaminating. The adhesive material 38 is heated and/or cured during thelaminating process forming the laminate structure 100 by a meanssuitable to the type of the adhesive material 38 being applied, whichmay include one or a combination of exposing the adhesive material 38 toelevated temperatures, for example, using flame bars, incinerator ovens,hot air ovens, etc., and/or hot melt, infrared, and ultraviolet systemsas understood by those knowledgeable in the field of laminating. Theexamples are non-limiting, and it would be understood that other formsof adhesive materials 38 such as dry powder or web forms, applicationmethods and curing processes may be used within the scope of forming thelaminate structure 100 including the aluminum sheets 12, 14 and the corelayer 10 described herein.

The adhesive material 38 forming the core layer 10 and/or the adhesivecore 16 is characterized by an elongation which is substantially greaterthan the elongation of the aluminum material comprising the aluminumsheets 12, 14, such that during deformation of the laminate structure100, for example, during stamping, extrusion, and/or bending of thelaminate structure 100 to form a component therefrom, the core layer 10remains in an elastic range and does not separate from the edges ofand/or between the aluminum sheets 12, 14 of the laminate structure 100,where it would be understood that separation of the adhesive core 16from the aluminum sheets 12, 14 would affect the damping characteristicsof the laminate structure 100 in the localized area where the separationoccurred. By way of non-limiting example, the core layer 10 and/or theadhesive core 16 is characterized by a minimum elongation of about 150%.In a preferred example, the core layer 10 and/or the adhesive core 16 ischaracterized by a minimum elongation of about 300%, and in a morepreferred example, an elongation in the range of about 300% to 400%.Preferably, a minimum elongation ratio of about ten (10) is maintainedfor the laminate structure 100, where the elongation ratio is expressedas the elongation of the core layer 16 relative to (divided by) theelongation of the thinner of the aluminum sheets 12, 14, to preventfracture of the core layer 16 and maintain the damping capacity of thelaminate structure 100. In a more preferred example, the laminatestructure 100 is characterized by a minimum elongation ratio of abouttwenty (20). In a most preferred example, the laminate structure 100 ischaracterized by a minimum elongation ratio in the range of about twenty(20) to thirty (30). In one example, the laminate structure 100 includes5XXX (series aluminum sheets 12, 14 each having a thickness T1, T2 of0.80 mm and an elongation in the range of about 18% to 22% and amodified rubber adhesive core 16 having a nominal thickness T3 of 0.025mm and an elongation of about 300% such that the example laminatestructure 100 is characterized by an elongation ratio of about 13.6 to16.7.

In a preferred example for forming the core layer 16 and laminatestructure 100, an adhesive material 38 is selected, applied to one orboth of the aluminum sheets 12, 14, cured and laminated to provide alaminate structure 100 which is characterized by an adhesive strength asmeasured by T-peel of at least ten pounds-force/inch (10 lbf/in orapproximately 1.75 Newtons/millimeter (N/mm)) using a T-peel strengthtest performed for example, in compliance with ASTM D1876 at a 10inch/minute pull rate, a lap shear strength of at least two mega Pascal(2 MPa) a lap shear strength test performed for example, in compliancewith ASTM D1002, a yield strength of 100-120 kilo-pounds per square inch(KSI) with an ultimate tensile strength of 200-250 KSI where plasticfailure of at least one of the aluminum sheets 12, 14 occurs prior toplastic failure of the adhesive core 16. In a most preferred example,the laminate structure 100 is characterized by an adhesive strength asmeasured by T-peel of at least fifteen foot-pounds/inch (15 lbf/in orapproximately 2.63 N/mm).

In a preferred example, the laminated structure 100 retains a minimum of80% of the original bond strength, as indicated by lap shear strengthand T-peel strength, after heat cycle aging, after thermal cycle (coldshock or cold/hot thermal cycling testing, for example, between −30degrees C. and +105 degrees C.) testing, and after cyclic corrosiontesting (for example, SAE J2334 testing), where the criteria for each ofthese is application specific for the intended use of the laminatestructure 100 or a component formed therefrom. In one example, thelaminate structure 100 is characterized by retaining greater than 80% ofthe original bond strength after being subjected to heat cycle aging at205 degrees Celsius for 40 minutes, to provide a laminate structure 100which can be subjected during a coating process cycle such aselectro-coating (electrostatic coating or E-coat) cycle or paintingcycle to a baking operation where the laminate structure 100 is heatedin a paint or e-coat oven in excess of 100 degrees Celsius and up to 205degrees Celsius, without degradation of the laminate structure 100 orcomponent formed therefrom. For example, such a laminate structure 100is suitable for forming into an automotive component such as a dashpanel, etc., which may be e-coated or painted. In the preferred example,the laminate structure 100 is able to withstand a 90 degree 1 T radiusbend at 0.75 inch flange length without degradation, where T is thethickness of the laminate structure 100 expressed in inches, where inthe present example the laminate structure 100 includes aluminum sheets12, 14 made of 5xxx series aluminum material and an adhesive core 16made of modified rubber, the laminate structure 100 having a totalthickness of approximately 0.072 inches. In a preferred example, alaminate structure 100 includes aluminum sheets 12, 14 made of 5xxxseries aluminum material with an “O” temper to provide high elongationwith relatively low tensile strength such that minimal springback occursduring and after forming of a component from the laminate structure 100,e.g., such that the laminate structure 100 exhibits formingcharacteristics similar to a deep draw grade ferrous material.

The laminate structure 100 exhibits a bending rigidity at roomtemperature (approximately 23 degrees Celsius) which is at least 35%that of a solid (monolithic) aluminum sheet having a thickness equal tothe combined thickness (T1+T2) of the aluminum sheets 10, 12. In apreferred example, the laminate structure 100 exhibits a bendingrigidity at room temperature of 50% or more relative to a monolithicaluminum sheet having a thickness equal to the combined thickness(T1+T2) of the aluminum sheets 10, 12. In a more preferred example, thelaminate structure 100 exhibits a minimum bending rigidity at roomtemperature of about 60% to 75% of that of a monolithic aluminum sheethaving a thickness equal to the combined thickness (T1+T2) of thealuminum sheets 10, 12.

As shown in FIG. 1, the core layer 10 may include one or moreintermediate coating or treatment layers 22, 24 which may be referred toherein as intermediate layers 22, 24. In the example shown, a firstintermediate layer 22 is disposed between the adhesive core 16 and thealuminum sheet 12 such that the intermediate layer 22 spanssubstantially the entirety of (i.e., is coextensive with) the aluminumsheet 12 and the adhesive core 16, and a second intermediate layer 24 isdisposed between the adhesive core 16 and the aluminum sheet 14 suchthat the intermediate layer 24 spans substantially the entirety of(i.e., is coextensive with) the aluminum sheet 14 and the adhesive core16. The example shown in FIG. 1 is non-limiting, and it would beunderstood that the laminate structure 100 may be constructed includingboth of the intermediate layers 22, 24, one of the intermediate layers22, 24, or neither of these. The intermediate layer 22, 24 prepares thesurface of the respective aluminum sheet 12, 14 to which it is applied,to passivate the surface of the aluminum sheet 12, 14 to increase thesurface bonding potential of the respective aluminum sheet 12, 14 tobond with the adhesive material 38 of the adhesive core 16, and/or toresist corrosion at the bond interface between the adhesive core 16 andthe respective aluminum sheet 12, 14 to prevent degradation of the bondbetween the adhesive core 16 and the respective aluminum sheet 12, 14,for example, by preventing formation of a corrosion product at the bondinterface.

The aluminum sheet 12, 14 may be prepared, e.g., pretreated, prior toapplying the intermediate layer 22, 24 by cleaning the aluminum sheet12, 14 with a deoxidation cleaner such as an alkaline cleaner or anacidic cleaner to remove soil, oil, grease, etc. from the surface of thealuminum sheet 12,14 and to remove any aluminum oxide product from thesurface of the aluminum sheet 12, 14, to prepare the surface of thealuminum sheet 12, 14 to receive the intermediate layer 22, 24. As such,the deoxidation cleaner creates a “fresh” aluminum surface which, if notsubsequently treated, e.g., coated, within a period of time, willreoxidize. As such, the deoxidation cleaner removes the oxide layer fromsurface of the aluminum sheet 12, 14 to temporarily increase bondingreceptivity of the aluminum sheet, for example, to one of the layers 22,24, 24, 32 described further herein. In a non-limiting example, thealuminum sheet 12, 14 may be cleaned and/or pretreated applying thecleaning solution using, for example, immersion cleaning, spraycleaning, rolling on the cleaning solution, or using other suitablechemical cleaning means to apply the deoxidation cleaner. In anotherexample, the aluminum sheet 12, 14 may be mechanically cleaned todeoxidize, e.g., remove the oxide layer from, the surfaces of thealuminum sheet 12, 14.

In one example, the intermediate coating 22, 24 may be applied at acoating weight thickness (CWT) in the range of about 2.0 to 10.0milligram/square meter (mg/m²) by spraying the intermediate coating 22,24 in solution form onto the aluminum sheets 12, 14 or immersing thealuminum sheets 12, 14 in the coating solution. In one example, theintermediate coating 22, 24 is applied as a solution containing titaniumand zirconium which passivates the aluminum surface of the aluminumsheet 12, 14, and prevents activation of the aluminum surface over time.In another example, the intermediate coating 22, 24 is applied as asolution containing tri-chromium oxide. The coating solution may also beapplied to the exterior surfaces, e.g., the outwardly facing surfaces,of the aluminum sheets 12, 14 to form exterior coating layers 28, 26, asshown in FIG. 2, to passivate and/or increase the surface bondingpotential of the exterior (outwardly facing) surface of the aluminumsheet 12, 14, as a pretreatment for further coating and/or painting ofthe laminate structure 100 or a component formed therefrom, and/or toprovide a corrosion prevention coating 26, 28 on the laminate structure100.

As shown in FIG. 3, an auxiliary coating layer 30, 32 may be appliedbetween the intermediate layer 22, 24 and the core layer 16 such thatthe auxiliary coating layer 30, 32 spans substantially the entirety of(i.e., is coextensive with) the core layer 16. Each of the auxiliarycoating layers 30, 32 may also be referred to herein as an auxiliarylayer 30, 32. In one example, the auxiliary layer 30, 32 may be atitanium and zirconium containing coating similar to the passivationlayer 22, 24, such that the laminate structure 100 includes first andsecond layers 22, 30 between the adhesive core 16 and the aluminum sheet12 and first and second layers 24, 32 between the adhesive core 16 andthe aluminum sheet 14, where the dual layering of the titanium-zirconiumcontaining layers 22, 30 and 24, 32 first passivates the aluminumsurface then increases the receptivity of bonding of the adhesive core16 to the aluminum sheet 12, 14. The increased receptivity provided bythe dual layering increases the bond strength at the bond interfacebetween the adhesive core 16 and the aluminum sheet 12, 14 resulting ina relatively higher peel strength, for example, greater than 10 lbf/in,while retaining the desired damping performance, for example, a CLF ofgreater than 0.1 within +/−10 degrees Celsius of the target operating(in use) temperature of the laminate structure 100 and/or a componentformed therefrom.

In one example, the laminate structure 100 may include at least one ofthe auxiliary layer 30, 32 which is a corrosion prevention layer toprevent contaminant ingression at the bonded interface between theadhesive core 16 and the adjacent aluminum sheet 12, 14, for example, bypreventing contaminant ingression at an exposed edge of the laminatestructure 100. In another example, the laminate structure 100 mayinclude at least one auxiliary layer 30, 32 configured as a thermalcoating to modify the thermal emissivity and/or thermal conductivity ofthe laminate structure 100. For example, at least one auxiliary layer30, 32 may be made of a heat dissipating material to dissipate heat awayfrom the adhesive core 16, or may be made of a heat absorptive materialto absorb heat into the laminate structure 100. In another example, thelaminate structure 100 may include at least one auxiliary layer 30, 32configured as an electrically conductive layer to modify the electricalconductivity of the laminate structure 100. For example, the laminatestructure 100 shown in FIG. 3 could include auxiliary layers 30, 32which are made of or include an electrically conductive material, suchas a carbon-based or graphite-based material or graphite film, and couldfurther include an adhesive core as shown in FIGS. 4 and 5, where theadhesive core 16 includes an electrically conductive filler 36 such thatthe adhesive core and the auxiliary layers 30, 32 are electricallyconductive and the laminate structure 100 is electrically conductive.The example shown in FIG. 3 is non-limiting, and it would be understoodthat the laminate structure 100 may be configured with one or bothauxiliary layers 30, 32, with a plurality of auxiliary layers 30disposed between the adhesive core 16 and the aluminum sheet 12, with aplurality of auxiliary layers 32 disposed between the adhesive core 16and the aluminum sheet 14, and/or without either auxiliary layer 30, 32.It would be understood that each of the auxiliary layers 30, 32 may besimilarly configured, e.g., be made of the same material and/or have thesame thickness, or may be differently configured, e.g., made ofdifferent materials and/or have different thicknesses and/or be includedto provide different functionalities (corrosion prevention, thermalconductivity, electrical conductivity, etc.) to the laminate structure100.

Referring to FIG. 2, the laminate structure 100 may include one or moreexterior coating layers 26, 28, which may be referred to herein asexterior coatings 26, 28 and/or as exterior layers 26, 28. In theexample shown, an exterior layer 28 is applied to, e.g., bonded,adhered, laminated or otherwise attached to, the exterior (outwardlyfacing or outermost) surface of the aluminum sheet 12 such that theexterior layer 28 spans substantially the entirety of (i.e., iscoextensive with) the aluminum sheet 12, and an exterior layer 26 isapplied to, e.g., bonded, adhered, laminated or otherwise attached tothe exterior (outwardly facing or outermost) surface of the aluminumsheet 14 such that the exterior layer 28 spans substantially theentirety of (i.e., is coextensive with) the aluminum sheet 12. Theexample shown in FIG. 2 is non-limiting, and it would be understood thatthe laminate structure 100 could be configured with one, both, orneither of the exterior layers 26, 28. The exterior coating layers 28,26 may be configured to passivate and/or increase the surface bondingpotential of the exterior (outwardly facing) surface of the aluminumsheet 12, 14, as a pretreatment for further coating and/or painting ofthe exterior surfaces of the laminate structure 100 or a componentformed therefrom, and/or to provide a corrosion prevention coating 26,28 on the laminate structure 100. The laminate structure 100 can includea plurality of exterior layers 26 and/or a plurality of exterior layers28 applied in a predetermined sequence. By way of non-limiting example,the laminate structure 100 could include a first exterior layer 28applied to, e.g., bonded, to the aluminum sheet 12, as a pretreatmentfor further coating and/or painting of the exterior (outwardly facing)surface of the aluminum sheet 12 with an additional exterior layer 28which may be, by way of non-limiting example, a paint layer, adecorative coating layer, a corrosion protection layer, a thermalcoating layer, etc. In one example, the exterior layer 26, 28 is a heatreflective thermal coating layer, such as a solar reflective layer, toreflect heat from and/or decrease heat absorption into the laminatestructure 100. In another example, the exterior layer 26, 28 is a heatabsorptive thermal coating layer, such as a low emissivity coating layeror black paint layer, to increase heat absorption into the laminatestructure 100.

In one example, at least one of the exterior layers 26, 28 may beconfigured as an isolation layer 34, as shown in FIG. 4, where an“isolation layer” as that term is used herein, is a layer of materialbonded to the laminate structure 100 to form an exterior layer of thelaminate structure 100, and configured to prevent corrosion of thelaminate structure 100 and/or to protect the aluminum layers 12, 14 towhich the isolation layer 34 is applied, for example, from chemicalattack and/or exposure to contaminants. In one example, the isolationlayer 34 is configured to prevent galvanic corrosion when the laminatestructure 100 and/or a component formed therefrom is in contact with,connected and/or fastened to a steel component. The isolation layer 34may also be referred to herein as a galvanic isolation layer 34. In oneexample, the galvanic isolation layer 34 can consist of a polymer binderwith zinc particles disbursed and embedded therein, with the polymerlayer preventing corrosion by preventing ion transfer through theisolation layer, and the zinc particles preferentially, e.g.,sacrificially, absorbing ions to prevent corrosion of the aluminum sheet12,14. The examples shown in the figures are non-limiting. For example,an exterior layer 26, 28 may be disposed between the aluminum sheet 14,12 and a galvanic isolation layer 34. By way of example, the galvanicisolation layer 34 may be applied to one or both exterior surfaces ofthe laminate structure 100. In one example, organic coatings, includingzinc rich primer coatings such as Granocoat® or Bonazinc™ and/ormodified epoxy or polyester based weldable paints and/or primers may beused to form the isolation layer 34.

By way of non-limiting example, a method of forming the laminatestructure 100 includes presenting the various layers required to formthe laminate structure 100 in the required sequence to a laminatingprocess which includes applying a laminating pressure to the sequencedlayers and curing the layered structure such that the layers are bondedtogether to form the laminate structure 100. By way of non-limiting andillustrative example and referring to FIG. 2, the laminate structure 100is formed by cleaning the aluminum sheets 12, 14, as previouslydescribed herein, to deoxidize the surfaces of the aluminum sheets 12,14. The inwardly facing surfaces of the aluminum sheets 12, 14, e.g.,the surfaces which are to be bonded to the adhesive core 16, arerespectively coated with the intermediate layers 22, 24, for example byspray, roller and/or immersion application of the coating materialforming the intermediate layers 22, 24, such that the coating materialcovers the entire surface of the aluminum sheet 12, 14, e.g., iscoextensive with the surface of the aluminum sheet 12, 14. In oneexample, coating material may be applied to the exterior (outwardlyfacing) surfaces of the aluminum sheets 12, 14 to form the exteriorlayers 28, 26, for example, by spray, roller and/or immersionapplication.

Still referring to the illustrative example shown in FIG. 2, and afterforming the intermediate layers 22, 24, the exterior layers 28, 26 onthe aluminum sheets 12, 14, the adhesive material 38 forming theadhesive core 16 is applied in two layers 18, 20, for example, byspraying or rolling, or may be applied as a dry adhesive film. Thealuminum sheet 12 and the aluminum sheet 14, sequenced as shown in FIG.2, are presented to the laminating process, e.g., to laminating rollssuch that the adhesive layers 18, 20 are facing, e.g., are brought incontact with each other, and laminated by applying a laminatingpressure, for example, via the laminating rolls, to form the laminatestructure 100. Alternately, as shown in FIG. 1 and previously describedherein, the adhesive material 38 forming the adhesive core 16 may beapplied in a single layer to one of the intermediate layers 22, 24. Thelaminate structure 100 is cured by elevating the temperature of thealuminum sheets 12, 14 and the adhesive core 16, for example, using oneor more ovens, flame bars, heated lamination rolls, etc. during and/orafter the lamination process forming the laminate structure 100.

Following the lamination process, e.g., after laminating and curing thesequenced layers forming the laminate structure 100, the laminatestructure 100 may be subjected to additional treatments, including, aspreviously described herein, the application of one or more of theexterior layers 26, 28, 34. The laminate structure 100 may be used toform components therefrom. For example, the laminate structure 100 maybe cut, stamped, pressed, bent, extruded, punched, drilled, etc. to forma component, where the component may define one or a combination of oneor more bends, fillets, chamfers, shoulders, openings, holes, slots,ribs, flanges, hems, etc. By way of non-limiting example, the laminatestructure 100 may be used to form a variety of structural componentswhich may be used in vehicles, such as a dash panel, package tray, panelshelf, seat panel, cowl panel, instrument panel frame, floor panel,tunnel panel, wheel well, back-up panel, trunk panel, etc. The examplesare non-limiting, and it would be understood that various componentswhich may be structural or non-structural components, may be formedusing the laminate structure 100 described herein.

Referring to FIGS. 4 and 5, the adhesive core 16 can include fillerparticles 36 distributed in the adhesive material 38 forming theadhesive core 16. The size, shape, configuration, material, density anddispersion pattern of the filler particles 36 may be selected to providea desired functional attribute of the core layer 10 and/or the adhesivecore 16. In one example, the adhesive core 16 is a phenolic modifiedrubber including a plurality of rubber filler particles 36. The phenolicbonds with the aluminum sheets 12, 14 and the rubber particles bond tothe phenolic, to contribute bond strength and peel strength, and to addviscoelastic damping performance to the laminate structure 100. Inanother example, the filler particles 36 may be configured to modify thethermal conductivity of the laminate structure 100.

In the example shown in FIG. 5, the filler particles 36 distributed inthe adhesive core 16 are electrically conductive to form an electricallyconductive core layer 10 and electrically conductive laminate structure100. For simplicity of illustration, the core layer 10 is shown in FIG.5 as consisting of the adhesive layer 16, and it would be understoodthat the core layer 10 may further include one or more intermediatelayers 22, 24 and/or one or more auxiliary layers 30, 32 as previouslydescribed herein. In the example shown, the filler particles 36 areprovided in a size and/or shape and are dispersed in the adhesive core16 at a density and/or dispersion pattern such that the electricallyconductive filler particles 36 provide a conductive path through theadhesive core 16 to form an electrically conductive laminate structure100. It would be appreciated that a uniform dispersion of fillerparticles 36 is desirable to provide a uniform conductive path throughthe laminate structure 100 when passing an electrical current throughthe laminate structure 100, for example, during a welding operation asshown in FIG. 5, to prevent electrical shunting and/or current jumping.Electrical shunting and/or current jumping could occur, for example, dueto a non-uniform dispersion of electrically conductive filler particles36 in the core layer 10, resultant for example from insufficient mixing,clumping, and/or settling of the filler particles 36 in the adhesivecore 16 during forming of the core layer 10. As such, the fillerparticles 36 may be coated, for example, with a wetting agent and/orsurfactant coating, to promote uniform mixing of the filler particles 36in the adhesive material 38 forming the adhesive core 16, and to preventsinking or clumping of the filler particles 36 in the core layer 10during forming of the laminate structure 100, such that a uniformdispersion of the filler particles 36 is maintained throughout thethickness of the core layer 10 after forming of the laminate structure100.

Referring to FIG. 5, shown is an illustrative welding operation forforming a weld in a weld zone 62 to join a laminate structure 100 tometal component 50, to form a welded assembly 60. In the non-limitingexample shown, the laminate structure 100 and metal component 50 arestacked and positioned between welding electrodes 52, such that eachwelding electrode 52 is in contact with a respective one of the laminatestructure 100 and the metal component 50 to define a weld zone 62therebetween. An electrical current is supplied to the electrodes 52such that current flows between the electrodes 52 through the weld zone62, via a current path determined by the aluminum sheets 12, 14, themetal component 50, and the conductive path defined by the dispersion offiller particles 36 in the core layer 10. The duration and magnitude ofthe current flow applied to the weld zone 62 is controlled such thatresistive heat is generated by the current flow through the aluminumsheets 12, 14, the metal component 50, and the dispersion of fillerparticles 36, to heat the materials in the weld zone 62 sufficiently topartially and preferably completely melt the metallic materials in theweld zone 62 to form a weld in the weld zone 62, which when solidifiedupon cooling joins the laminate structure 100 and the metal component 50to form the welded assembly 60. A resistive welding process is shown inthe FIG. 5 as an illustrative example, and it would be understood any ofvarious conventional welding processes could be used to join thelaminate structure 100 described herein to another metal component,including without limitation resistive welding processes including spotwelding, seam welding, flash welding, projection welding, upset welding;energy beam welding including laser beam welding, electron beam welding,laser hybrid welding; gas welding including oxyfuel welding; arc weldingincluding gas metal arc welding, metal inert gas welding, or shieldedmetal arc welding.

In the illustrative example, the metal component 50 may be, for example,a monolithic component made of a metal such as aluminum or other metalweldable to the laminate structure 100. In another example, the metalcomponent 50 may be a laminate structure such as a laminate structure100 described herein. For simplicity of illustration, the exampleillustrated in FIG. 5 shows two components 100, 50 stacked for weldingto form the welded assembly 60. This example is non-limiting, and itwould be understood that multiple components, e.g., three or moreincluding at least one component formed as a laminate structure 100,could be stacked and positioned between the weld electrodes 52 andjoined by forming a weld between the three or more components in theweld zone 62.

In the illustrative examples described herein, except for the firstexample, the electrically conductive filler particles 36 are composed ofat least two filler materials, illustratively shown in FIG. 5 as fillermaterials 54, 56, 58 where each of the filler materials 54, 56, 58 isdifferent from another of the filler materials 54, 56, 58. The firstexample described herein illustrates the inability to weld a laminatestructure 100 where the filler particles 36 are made of a single fillermaterial, which in the illustrative first example is aluminum. Theremaining examples are illustrative that a weld is formable in alaminate structure 100 with filler particles 36 comprised of twodifferent materials 54, 56, and of three different materials 54, 56, 58.The examples are non-limiting, and it would be understood that thefiller particles 36 could be made of more than three different fillermaterials. The filler particles 36 are configured and dispersed in theadhesive core 16 at an additive level to meet at least two criteria forproper weld formation. As a first criteria, the filler particles 36should be configured and dispersed in the adhesive core 16 at anadditive level to provide an electrically conductive path throughadhesive core 16 which is characterized by sufficient resistivity togenerate the resistive heat required to melt material in the weld zone62 during weld formation, while exhibiting sufficient conductivity toallow current passage without expulsion or formation of weld faultsduring the welding process, to form an “acceptable weld.” For example,the filler particles 36 should be dispersed in the core material 38 suchthat clumping and/or settling of the filler particles 36 is avoided, toavoid shunting and/or current jumping outside of the weld zone 62. An“acceptable weld” as that term is used herein, is a weld which will meetthe performance requirements of the welded assembly 60, including forexample, weld nugget size, weld shear strength, fatigue resistance,corrosion resistance including resistance to corrosion after processingto apply E-coat, and resistance to galvanic corrosion. An “acceptableweld” is characterized by an absence of or substantially no welddiscontinuities, including an absence of or substantially no porosity,weld cracking, or other discontinuities, such as the formation of oxidesor intermetallic compounds in the weld, which may negatively impact weldperformance or integrity.

The second criteria for configuration of the filler particles 36 isalloying compatibility with the aluminum of the aluminum sheets 12, 14during weld formation, e.g., the filler particles 36 should beconfigured and dispersed in the adhesive core 16 at an additive levelwhich will, when combined with aluminum from the aluminum sheets 12, 14,form an acceptable weld. The filler particles 36 may be provided at anadditive level which is controlled to provide, increase, and/or enhancecharacteristics of the weld which are favorable to formation of anacceptable weld. For example, one of the filler materials 54, 56, 58 maybe copper, manganese or magnesium, included at an additive level whichenhances one or more of weld ductility, strength, and/or corrosionresistance.

One or more of the filler materials 54, 56, 58 forming the fillerparticles 36 may be provided at an additive level which is controlled ata balanced level to provide a beneficial effect, such as increasingresistivity of the filler particle 36, while preventing a detrimentaleffect, such as an alloying incompatibility. For example, one of thefiller materials 54, 56, 58 may be iron or nickel, included at asufficient additive level to increase resistivity however controlled ata sufficiently low additive level to prevent the formation ofintermetallic compounds in the resulting weld.

The filler particles 36 can include two or more filler materials 54, 56,58 provided in various configurations to satisfy the criteria describedabove. By way of non-limiting example, a filler particle 36 may beprovided as a compound formed of the two or more filler materials 54,56, 58, a mixture, such as a powder mixture, of two or more fillermaterials 54, 56, 58, coated particles where the particle may be formedof a first filler material 54 and coated with a second filler material56. The filler particles 36 may be provided as a mixture of a firstfiller particle made of one or more of the filler materials 54, 56, 58,a second filler particle made of one or more of the filler materials 54,56, 58 where at least one of the composition, configuration, and/oradditive level of the second filler particle is different from thecomposition, configuration and/or additive level of the first fillerparticle. In this example, the mixture may include a third, fourth, etcfiller particle of a different composition than each of the first andsecond filler particles.

A third criteria is the volume of filler particles 36 in the adhesivecore 16. As the volume of filler particles 36 increases in the adhesivecore 16, the bond strength may decrease proportionally. In one example,the criteria for the volume of filler particles 36 is to limit thevolume of filler particles 36 in the adhesive core 16 to a level suchthat the bond strength of the laminate structure 100 including thefiller particles 36 is at least 90% of the bond strength of the laminatestructure 100 formed without the filler particles 36. The volume offiller particles 36 in the core layer 10 can be expressed as a volumepercentage and/or as a corresponding weight percentage based on theconfiguration and density of the filler particles 36. In one example,the volume of electrically conductive filler particles 36 is preferablyless than 18% of the total volume of the core layer 10 and less than 50%of the total weight of the core layer 10. In a more preferred example,volume of electrically conductive filler particles 36 is preferably lessthan 10% of the total volume of the core layer 10 and less than 30% ofthe total weight of the core layer 10.

EXAMPLES Example 1

Example 1 is a laminate structure 100 including a core layer 10including filler particles 36 made of aluminum material containing atleast 99.8% aluminum (Al), such that the material chemistry and theelectric potential of the filler particles 36 are substantially similarto that of the aluminum sheets 12, 14. The aluminum filler particles 36are distributed in the adhesive material 36 at an additive levelexpressed as a percentage weight of the adhesive core 16 in the range ofabout 5% to 20%, and preferably, at a percentage weight in the range ofabout 5% to 10%. In this example, the laminate structure 100 having atotal thickness T (T1+T2+T3) as shown in FIG. 1) was stacked to a solidaluminum component 50 made of 6061-T6 aluminum alloy having a thicknessof 0.8 mm and current was supplied to weld electrodes 62 in contact witheach of the laminate structure 100 and the solid aluminum component 50.Surprisingly, current does not pass through the laminate structure 100containing the aluminum filler particles 36, and no weld is formed. Itwas observed that exposure of the aluminum filler particles 36 priorand/or during addition of the filler particles 36 to the adhesivematerial 38 could result in formation of an electrically insulatingaluminum oxide on the surface of the filler particles 36, preventingcurrent flow and preventing weld formation.

Example 2

Example 2 is a laminate structure 100 including a core layer 10including filler particles 36 made of a first filler material 54 whichis aluminum (Al) and a second filler material 56 which is zinc (Zn). Thefiller particles 36 are configured as aluminum particles which arecoated with zinc using a zincating process. During the zincatingprocess, the aluminum particles are deoxidized prior to coating with thezinc, such that aluminum oxide is not present in the filler particles36. The aluminum and the zinc are electrically conductive and zinc has arelatively higher resistivity than aluminum, such that the fillerparticles 36 made of zincated (zinc coated) aluminum particles providean electrically conductive path through the core layer 10, which hassufficiently high resistivity to generate heat when electrical currentis passed through the laminate structure 100 during a welding operation.The zincated aluminum filler particles 36 are distributed in theadhesive material 36 at an additive level expressed as a percentageweight of the adhesive core 16 in the range of about 5% to 37.5% of thetotal weight of the adhesive core 16, and preferably, at a percentageweight in the range of about 15% to 25% of the total weight of theadhesive core 16. The volume of zincated aluminum filler particles 36distributed in the core layer 10 is within the range of about 6% to 15%of the total volume of the core layer 10, and preferably within therange of about 6% to 10% of the total volume of the core layer 10. Inthis example, the laminate structure 100 having a total thickness T(T1+T2+T3 as shown in FIG. 1) is welded to a solid aluminum component 50made of 6061-T6 aluminum alloy having a thickness of 0.8 mm by passingcurrent through the stacked laminate structure 100 and aluminumcomponent 50 to form an acceptable weld nugget.

Example 3

Example 3 is a laminate structure 100 including a core layer 10including filler particles 36 made of a first filler material 54 whichis iron (Fe) and a second filler material 56 which is phosphorus (P).The filler particles 36 are configured as a compound form of ironphosphides (FeP, Fe2P) provided as a powder having a particle size of inthe range of about 5 micron to 125 micron, with a median particle sizeof about 25 micron. The iron is electrically conductive and has arelatively higher resistivity than aluminum, such that the fillerparticles 36 made of the iron phosphorus compound provide anelectrically conductive path through the core layer 10, which hassufficiently high resistivity to generate heat when electrical currentis passed through the laminate structure 100 during a welding operation.Of significance, both iron and phosphorus have very low solubility inaluminum in the solid state (˜0.04% for iron and <0.01% for phosphorus),such that both iron and phosphorus are considered an impurity inaluminum. Unexpectedly, when the additive level of the filler particles36, e.g., the additive level of the iron and phosphorus filler materialsin combination, is controlled for alloying compatibility at a percentageweight in the range of about 12% to 49% of the adhesive core 16, andpreferably, at a percentage weight in the range of about 20% to 30%, thelaminate structure 100 is weldable to a solid (monolithic) aluminumcomponent 50 to form an acceptable weld nugget. Surprisingly, the weldnugget is formed without propagation of iron phosphorus out of the weldin a sufficient quantity to cause adverse effects to the weld nugget,suggesting the iron and phosphorus at this additive level remains insolution in the weld nugget thus formed. In this example, the laminatestructure 100 having a total thickness T (T1+T2+T3 as shown in FIG. 1)is welded to a solid aluminum component 50 made of 6061-T6 aluminumalloy having a thickness of 0.8 mm by passing current through thestacked laminate structure 100 and aluminum component 50 to form a weldnugget measuring between 3.5 mm and 5 mm, using an alternating current(AC) resistance welder. No shunting of current between the outer layers12, 14 of the laminate structure 10 is observed. Minimal discontinuitiesare observed during visual examination of a cross-section of the weldnugget. Tensile shear data showed all welds tested broke in the parentmetal in the heat affected zone (HAZ). Corrosion testing of coated andnon-coated welded assemblies shows no corrosion which would bedetrimental to weld integrity.

Example 4

Example 4 is a laminate structure 100 including a core layer 10including filler particles 36 made of a first filler material 54 whichis zinc (Zn) and a second filler material 56 configured as a pluralityof hollow carrier objects. The filler particles 36 are provided as thecarrier objects coated with zinc. The carrier objects in this exampleare hollow glass spheres. The zinc is electrically conductive and has arelatively higher resistivity than aluminum, such that the fillerparticles 36 made of the zinc coated glass spheres provide anelectrically conductive path through the core layer 10, which hassufficiently high resistivity to generate heat when electrical currentis passed through the laminate structure 100 during a welding operation.The additive level of zinc coated glass spheres (filler particles 36) iscontrolled for alloying compatibility at a percentage weight in therange of about 8% to 30% of the adhesive core 16, and preferably, at apercentage weight in the range of about 10% to 20%, and the laminatestructure 100 is weldable to a solid (monolithic) aluminum component 50to form an acceptable weld nugget. In this example, the laminatestructure 100 having a total thickness T (T1+T2+T3 as shown in FIG. 1)is welded to a solid aluminum component 50 made of 6061-T6 aluminumalloy having a thickness of 0.8 mm by passing current through thestacked laminate structure 100 and aluminum component 50 to form a weldnugget measuring between 3.5 mm and 5 mm, using an alternating current(AC) resistance welder. No shunting of current between the outer layers12, 14 of the laminate structure 10 is observed. In this example, thediameter of the zinc coated glass spheres ranged in size from a diametersubstantially the same thickness (T3 in FIG. 1) of the adhesive core 16,which in the present example is 30 microns, or less. The zinc coating onthe glass spheres having a diameter of 30 microns, e.g., having adiameter substantially equal to the thickness of the adhesive core 16,provided a conductive bridge between the first and second aluminumlayers 12, 14 to define a conductive path through the laminate structure100. Zinc coated glass spheres having a diameter of less than 30 micronsare distributed in the adhesive core 16 such that a conductive path isdefined by the points of closest contact between adjacent spheres. Thelaminate structure 100 is advantaged by a lower density provided by thehollow glass spheres, which also contribute to increased rigidity andcrush resistance of the core layer 10.

Example 5

Example 5 is prepared using the same method as Example 4, except thefirst filler material 54 is a silver (Ag) coating applied to the hollowglass spheres forming the second filler material 56, to provide fillerparticles 36 configured as silver coated glass spheres. An acceptableweld nugget measuring between 3.5 mm and 5 mm, using an alternatingcurrent (AC) resistance welder is formed. No shunting of current betweenthe outer layers 12, 14 of the laminate structure 10 is observed.

Example 6

Example 6 is prepared using the same method as Example 4, except thefirst filler material 54 is a nickel (Ni) coating applied to the hollowglass spheres forming the second filler material 56, to provide fillerparticles 36 configured as nickel coated glass spheres. An acceptableweld nugget measuring between 3.5 mm and 5 mm, using an alternatingcurrent (AC) resistance welder is formed. No shunting of current betweenthe outer layers 12, 14 of the laminate structure 10 is observed.

Example 7

Example 7 is a laminate structure 100 including a core layer 10including filler particles 36 made of a first filler material 54 whichis magnesium (Mg) and a second filler material 56 which is magnesiumoxide (MgO). The filler particles 36 are configured as a mixture ofmagnesium particles and magnesium oxide particles. The magnesium iselectrically conductive and has a relatively higher resistivity thanaluminum, and the magnesium oxide has a high resistivity such that thefiller particles 36 made of the mixture of magnesium particles andmagnesium oxide particles provide an electrically conductive paththrough the core layer 10 which has sufficiently high resistivity togenerate heat when electrical current is passed through the laminatestructure 100 during a welding operation. Magnesium has good alloyingcompatibility with aluminum, with excellent weldability and is not proneto hot-cracking. In this example, the laminate structure 100 having atotal thickness T (T1+T2+T3 as shown in FIG. 1) is welded to a solidaluminum component 50 made of 6061-T6 aluminum alloy having a thicknessof 0.8 mm by passing current through the stacked laminate structure 100and aluminum component 50 to form an acceptable weld nugget which isabsent of porosity and crack free.

Example 8

Example 8 is prepared using the same method as Example 7, except thesecond filler material 56 is manganese dioxide (MnO₂). The fillerparticles 36 are configured as a mixture of magnesium particles andmanganese dioxide particles. Manganese dioxide has a high resistivitysuch that the filler particles 36 made of the mixture of magnesiumparticles and manganese dioxide particles provide an electricallyconductive path through the core layer 10 which has sufficiently highresistivity to generate heat when electrical current is passed throughthe laminate structure 100 during a welding operation. Manganese hasgood alloying compatibility with aluminum, with good weldability,providing good ductility and improved corrosion properties to the weld.An acceptable weld nugget which is absent of porosity and crack free isformed using this Example.

Example 9

Example 9 is a laminate structure 100 including a core layer 10including filler particles 36 made of mixture of a first filler material54 which is manganese dioxide (MnO₂), a second filler material 56 whichis magnesium (Mg), and a third filler material 58 which is aluminum(Al). The filler particles 36 are mixed to form a powder. The magnesiumand aluminum have good electrical conductivity. The magnesium and themanganese dioxide have relatively higher resistivity than aluminum, suchthat the filler particles 36 made of the mixture of manganese dioxide,magnesium and aluminum provide an electrically conductive path throughthe core layer 10, which has sufficiently high resistivity to generateheat when electrical current is passed through the laminate structure100 during a welding operation. As described for Examples 6 and 7, bothmagnesium and manganese have good alloying compatibility with aluminum.The additive level of filler particles 36, e.g., the additive level ofthe mixture of filler materials 54, 56, 58 is at a percentage weight inthe range of about 12% to 49% of the adhesive core 16, and preferably,at a percentage weight in the range of about 20% to 30%, and thelaminate structure 100 is weldable to a solid (monolithic) aluminumcomponent 50 to form an acceptable weld nugget. In this example, thelaminate structure 100 having a total thickness T (T1+T2+T3 as shown inFIG. 1) is welded to a solid aluminum component 50 made of 6061-T6aluminum alloy having a thickness of 0.8 mm by passing current throughthe stacked laminate structure 100 and aluminum component 50 to form aweld nugget measuring between 3.5 mm and 5 mm, using an alternatingcurrent (AC) resistance welder. No shunting of current between the outerlayers 12, 14 of the laminate structure 10 is observed.

Example 10

Example 10 is prepared using the same method as Example 9, except thesecond filler material 56 is silicon (Si), which has relatively higherresistivity than aluminum, such that the filler particles 36 made of themixture of manganese dioxide, silicon and aluminum provide anelectrically conductive path through the core layer 10, which hassufficiently high resistivity to generate heat when electrical currentis passed through the laminate structure 100 during a welding operation.A weld nugget measuring between 3.5 mm and 5 mm was formed, and noshunting of current between the outer layers 12, 14 of the laminatestructure 10 is observed.

Example 11

Example 11 is prepared using the same method as Example 9, except thethird filler material 58 is zinc, which has relatively higherresistivity than aluminum and good alloying compatibility with aluminum,such that the filler particles 36 made of the mixture of manganesedioxide, silicon and zinc provide an electrically conductive paththrough the core layer 10, which has sufficiently high resistivity togenerate heat when electrical current is passed through the laminatestructure 100 during a welding operation. A weld nugget measuringbetween 3.5 mm and 5 mm was formed, and no shunting of current betweenthe outer layers 12, 14 of the laminate structure 100 is observed.

The illustrative examples provided by the description herein and therelated figures are non-limiting, and it would be understood that aplurality of alternative configurations of the layers of the laminatestructure 100 exist within the scope of the description incorporatingvarious combinations of the metal sheets 12, 14, configurations of thecore layer 10, various configurations of the adhesive core 16, variousconfigurations of the filler particles 36, various combinations and/orconfigurations of the filler materials 54, 56, 58 comprising the fillerparticles 36, and various combinations and/or configurations of one ormore of intermediate layers 22, 24, auxiliary layers 30, 32, exteriorlayers 26, 28, separating layers 34, and/or filler particles 36 toprovide a laminate structure 100 characterized by a combination ofproperties and/or features as required by the specified applicationand/or use of the laminate structure 100 and/or a component formedtherefrom. The Examples provided herein are illustrative and theteachings provided by the Examples envision that similar results areexpected when any of the values provided in the examples are variedwithin the ranges provided, and envision that similar results areexpected by substitution of materials having substantially similarproperties, for example, substantially similar electrical propertiessuch as resistivity and conductivity, as those noted above. By way ofillustration, referring to Example 7, it is envisioned that similarresults as to weldability of the laminate 100 can be achieved usingfiller particles 36 comprised of a first conductive metal 54 which showsgood alloying compatibility with aluminum, such as one or more of agroup consisting of manganese, aluminum (deoxidized), zinc, silicon andcopper, and a second conductive metal 56 which is the oxidizedcounterpart of the metal 54. For example, a laminate structure 100including particles 36 comprising a mixture of zinc and zinc oxide isenvisioned to be weldable to form a weld nugget without shunting. Inanother illustrative example, referring to Example 2, it is envisionedthat the aluminum particles could be coated with another conductivematerial other than zinc, to provide filler particles 36 to form alaminate structure which is weldable. In yet another illustrativeexample, referring to Example 4, it is envisioned that the hollowcarrier objects may be provided in a shape other than a sphere, e.g.,for example, could be provided in a non-spherical ovoid shape, as acylinder, rod, ellipsoid, etc. or other shape capable of currentbridging the first and second aluminum layers 12, 14 and/or nesting incontact to provide a conductive path between the first and secondaluminum layers 12, 14 when coated with a conductive material. Referringagain to Example 4, it is envisioned that the hollow carrier objects canbe formed of materials other than glass, for example, ceramic basedmaterials, and/or that the conductive material coating the glass spheremay be another material which satisfies the criteria for electricalconductivity and resistance and alloying compatibility, such as nickel.

The combination of properties and/or features for which a laminatestructure 100 is configured includes a combination of one or more of NVHproperties, damping, elongation, tensile strength, shear strength,formability, peel strength, corrosion prevention, thermal properties,electrical conductivity, and/or weldability. The example configurationsof laminate structures 100 shown in FIGS. 1-5 are non-limiting, and itwould be understood that the various layers shown in the figures may bealternatively combined to provide other configurations of the laminatestructure 100 not shown in the figures but included in the scope of thedescription.

The detailed description and the drawings or figures are supportive anddescriptive of the present teachings, but the scope of the presentteachings is defined solely by the claims. While some of the best modesand other embodiments for carrying out the present teachings have beendescribed in detail, various alternative designs and embodiments existfor practicing the present teachings defined in the appended claims.

1. A laminate structure comprising: a first metal sheet; a second metalsheet; wherein the first and second metal sheets are made of an aluminumbased material characterized by an aluminum electrical resistivity; anadhesive core; wherein the adhesive core is disposed between and bondedto the first and second metal sheets such that the adhesive core iscoextensive with each of the first and second metal sheets; wherein thefirst metal sheet, the second metal sheet, and the adhesive core arelaminated together to form the laminate sheet; wherein the adhesive coreincludes a plurality of electrically conductive filler particlesdispersed in an adhesive material; wherein the filler particles are madeof a first filler material and a second filler material which is adifferent material than the first filler material; wherein at least onethe first and second filler materials has a filler electricalresistivity greater than the aluminum electrical resistivity; whereinthe plurality of electrically conductive filler particles defines aconduction path by which an electrical current applied to one of thefirst and second metal sheets is conducted through the adhesive core tothe other of the first and second metal sheets to generate a resistiveheat; and wherein a percentage weight of the filler particles is in arange of about 5% to 49% of a total weight of the adhesive core.
 2. Thelaminate structure of claim 1, wherein the resistive heat is sufficientto at least partially melt the first and second metal sheets in a weldzone including the conduction path.
 3. The laminate structure of claim1, wherein: the first filler material is a first iron phosphidecompound; the second filler material is second iron phosphide compound;and the first iron phosphide compound is different than the second ironphosphide compound.
 4. The laminate structure of claim 1, wherein: thefirst filler material is zinc; the second filler material is aluminumparticles; and wherein the filler particles are formed by coating thealuminum particles with the zinc.
 5. The laminate structure of claim 4,wherein the aluminum particles are deoxidized prior to being coated bythe zinc.
 6. The laminate structure of claim 4, wherein a percentageweight of the filler particles is in a range of about 5% to 37.5% of atotal weight of the adhesive core.
 7. The laminate structure of claim 1,wherein: the first filler material is one of zinc, silver, and nickel;the second filler material is a plurality of carrier objects; andwherein the filler particles are formed by coating the carrier objectswith the one of the zinc, silver, and nickel.
 8. The laminate structureof claim 7, wherein the carrier object is made of one of a glass and aceramic material.
 9. The laminate structure of claim 8, wherein thecarrier object is a hollow object.
 10. The laminate structure of claim7, wherein the carrier object is a spherical object having an objectdiameter; wherein the adhesive core has a core thickness; and whereinthe core thickness and the object diameter are substantially the same.11. The laminate structure of claim 7, wherein a percentage weight ofthe filler particles is in a range of about 8% to 30% of a total weightof the adhesive core.
 12. The laminate structure of claim 1, wherein:the first filler material is one of magnesium, zinc, silicon, andcopper; and the second filler material is an oxide of the one ofmagnesium, zinc, silicon, and copper.
 13. The laminate structure ofclaim 1, wherein: the first filler material is magnesium; the secondfiller material is manganese dioxide.
 14. The laminate structure ofclaim 1, wherein the filler particles include a third filler materialwhich is a different material than the first and second fillermaterials.
 15. The laminate structure of claim 14, wherein: the firstfiller material is manganese dioxide; the second filler material ismagnesium and silicon; and the third filler material is one of aluminumand zinc.
 16. A method of welding a laminate structure, the methodcomprising: providing a laminate structure, wherein the laminatestructure includes: a first metal sheet; a second metal sheet; whereinthe first and second metal sheets are made of an aluminum based materialcharacterized by an aluminum electrical resistivity; an adhesive core;wherein: the adhesive core is disposed between and bonded to the firstand second metal sheets such that the adhesive core is coextensive witheach of the first and second metal sheets; the first metal sheet, thesecond metal sheet, and the adhesive core are laminated together to formthe laminate sheet; the adhesive core includes a plurality ofelectrically conductive filler particles dispersed in an adhesivematerial; the filler particles are made of a first filler material and asecond filler material which is a different material than the firstfiller material; and at least one the first and second filler materialshas a filler electrical resistivity greater than the aluminum electricalresistivity; wherein the plurality of electrically conductive fillerparticles defines a conduction path by which an electrical currentapplied to one of the first and second metal sheets is conducted throughthe adhesive core to the other of the first and second metal sheets togenerate a resistive heat; wherein a percentage weight of the fillerparticles is in a range of about 5% to 49% of a total weight of theadhesive core; providing a metal component; stacking the laminatestructure and the metal component; flowing an electrical current througha weld zone defined by the stacked laminate structure and the metalcomponent; wherein the plurality of electrically conductive fillerparticles defines a conduction path by which the electrical current isconducted through the adhesive core to generate a resistive heat; andwherein the resistive heat is sufficient to at least partially melt thefirst and second metal sheets and the metal component to form a weld inthe weld zone.
 17. A laminate structure comprising: a first metal sheet;a second metal sheet; wherein the first and second metal sheets are madeof an aluminum based material characterized by an aluminum electricalresistivity; an adhesive core; wherein the adhesive core is disposedbetween and bonded to the first and second metal sheets; wherein theadhesive core includes a plurality of electrically conductive fillerparticles dispersed in an adhesive material; wherein the fillerparticles are made of a first filler material and a second fillermaterial; wherein the first filler material is one of magnesium, zinc,silicon, and copper; wherein the second filler material is an oxide ofthe one of magnesium, zinc, silicon, and copper; and wherein theplurality of electrically conductive filler particles defines aconduction path by which an electrical current applied to one of thefirst and second metal sheets is conducted through the adhesive core tothe other of the first and second metal sheets to generate a resistiveheat.